Typical prior art point to multipoint communication systems comprising a base station and plural remote stations typically adjust the gain of the transmitter on each remote station to the same value. The value for transmitter gain is typically based on the distance of the furthest remote from the base station, i.e., the highest gain value, so that the base station is ensured to be able to communicate with the furthest remote. Setting transmitter gain to an identical value for all remote stations in a communication system is common practice for prior art broadband wireless access systems. Such a prior art transmitter gain scheme allows for communications between the furthest remote and the base station without having to modify individual transmitters when the remote station transmitters are placed in the field. While this scheme allows for commonality between all the remote station transmitters in the communication system, the scheme results in a poor inband noise figure for the receiver at the base station thereby limiting the number of remote stations that can communicate with the base station.
One embodiment of the present invention avoids the problems of the prior art by the use of a novel wireless point to multipoint communication system which maximizes the number of remote stations capable of communicating with a base station. The present invention allows for more remote stations by minimizing the inband noise floor of the base station receiver.
The inband noise floor of the base station receiver is affected by, among other things, the strength of the signals in the frequency band of interest received from the remote stations with which the base station communicates. Prior art systems adjust the gain of the remote station transmitters to be the same value regardless of the distance between an individual remote station and the base station. The gain is typically set at a value to allow the remote station that is furthest from the base station to be able to communicate with the base station, which results in a gain setting for the other remote stations that are closer to the base station than the furthest remote station to have a transmitter gain setting that is higher then necessary to communicate with the base station. The higher gain setting for the closer-in remote stations results in an xe2x80x9cexcess inband signal strengthxe2x80x9d seen by the receiver at the base station from the closer-in remote stations. The excess inband signal strength causes the inband noise floor of the base station receiver to increase. This increase in the inband noise floor effectively limits the number of remote stations with which the base station can communicate.
The present invention discloses a system and method for independent gain control of the transmitter on a particular remote station as a function of the distance between that remote station and the base station. Independent gain control eliminates the excess inband signal strength thereby allowing for an increase in the number of remote stations with which the base station can communicate. One embodiment of the present invention accomplishes gain control of the remote station transmitters by including attenuators in the RF transmit circuit of the remote stations. Any number of attenuators may be added to the RF transmit circuit as contemplated by the present invention. The attenuators may be placed anywhere in the RF transmit circuit but preferentially are placed immediately preceding the RF power amplifier in the RF transmit circuit. The amount of attenuation that the attenuators may add to the RF transmit circuit may be variable and may be controlled by a microprocessor. In one embodiment of the present invention, a value representing the amount of attenuation to be applied to a remote station transmitter is input into a look up table at the remote station. A microprocessor at the remote station accesses the value in the look up table and sends a control signal to an attenuator in the RF signal path of the remote station transmitter to control the amount of attenuation that the attenuator adds to the RF signal path. Therefore, the amount of attenuation added to the RF signal path is a function of the distance between the remote station and the base station.
Accordingly, it is an object of the present invention to provide a novel wireless point to multipoint communication system where ones of plural remote stations utilize transmitter gain control.
It is another object of the present invention to provide a novel wireless point to multipoint communication system where ones of plural remote stations utilize transmitter gain control as a function of the distance of the remote to the base station.
It is yet another object of the present invention to provide a novel wireless point to multipoint communication system where gain control of the remote stations is achieved by placing high frequency attenuators in the RF transmit path.
It is still another object of the present invention to provide a novel RF transmission circuit where controllable attenuators are placed in the RF transmit path immediately preceding the RF amplifiers.
It is a further object of the present invention to provide a novel RF transmission circuit where a microprocessor controls the amount of attenuation of attenuators placed in the RF transmit path.
It is yet a further object of the present invention to provide a novel wireless point to multipoint communication system for millimeter wave communication signals where ones of plural remote stations utilize transmitter gain control.
It is still a further object of the present invention to provide a novel wireless point to multipoint communication system for transmitting communication signals in the 3.4 to 3.7 GHz frequency range where ones of plural remote stations utilize transmitter gain control as a function of the distance of the remote to the base station.
It is an additional object of the present invention to provide a novel wireless point to multipoint communication system for millimeter wave communication signals where ones of plural remote stations utilize transmitter gain control to maximize the number of remote stations that can communicate with a base station.
It is yet an additional object of the present invention to provide a novel wireless point to multipoint communication system for millimeter wave communication signals where ones of plural remote stations utilize transmitter gain control to maximize the number of remote stations that can communicate with a base station by minimizing the noise floor of the receiver at the base station.
It is still an additional object of the present invention to provide a novel wireless point to multipoint communication system where ones of plural remote stations utilize transmitter gain control as a function of the distance of the remote to the base station where the gain control of the transmitter of each remote station can be adjusted independently of the gain control of the transmitter of other remote stations.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.